You aren't going to do a move as much as a copy so I would try the following. Refer to the linked article for detailed steps.

1) Download the wp-contents folder from the dev site
2) Install WordPress under the root. Leave /dev alone for now.
3) Create a new database for the top-level site.
4) Upload the wp-contents folder to the new top-level site to get the theme/graphics/plugins in place
5) Export the dev database as a mysql dump file. Do a search and replace on the dump file to remove references to /dev/
6) Import the revised dump to the database created at step 3

That should "move" the dev to live and mostly work. You may have to deactivate and reactivate plugins and permalinks to get the .htaccess file to regenerate properly.

For changing /dev/ to /esp/, all you really need to do is change /dev/ to /esp/ in the database and then rename the directory. My article provides the relevant MySQL queries that will do this for you.